This invention relates generally to the field of medical compression and distraction devices in the field of bone fixation, repair and regeneration, and more particularly relates to such devices and methods utilized in osteogenesis, such as with maxillary craniofacial repair, facial or cranial reconstruction, or treatment for congenital, developmental and traumatic defects.
It is often desirable or necessary to effect reconstruction or repair of the craniofacial bones defining the face or cranium of a person, such as for example the midface, the mandible and/or the maxilla. This need may arise from congenital conditions, developmental disorders or trauma. In many circumstances the abnormalities are corrected by first performing an osteotomy, i.e., cutting or fracturing a bone to create two segments separated by a gap or space. In some instances the bone segments will be shifted into the proper orientation and alignment, and then fixed in place relative to each other until bone growth across the gap (osteogenesis) results in the formation of a unitary bone member. In other instances it is necessary to lengthen the original bone member, in which case after the osteotomy devices known as distractors are utilized to incrementally lengthen the bone.
A distractor is a device that has affixation members, such as bone plates, that are joined to each of the bone segments on opposite sides of the osteotomy. The device further includes a distraction mechanism, such as a rotatable threaded rod for example, that enables the distance between the bone plates to be slowly increased over time, thereby allowing new bone growth to occur between the bone segments. The new bone growth increases in dimension until the proper bone length is achieved, at which time the distraction process is halted and the distractor is removed after sufficient healing time. The distraction mechanism is usually actuated by a separate tool, such as a screw-driver like hand tool having a polygonal socket which mates with an exposed polygonal tip on the proximal end of the distractor (the end most accessible to the surgeon) or a polygonal tip which mates with an exposed polygonal socket on the proximal end of the distractor. The osteogenesis process comprises separating the bone plates a short distance, allowing bone growth to fill in the gap, separating the bone plates a short distance again, allowing the bone growth to occur, etc., with the process repeated until the desired bone configuration is achieved.
As a typical example, it is often desired to advance the midface or maxillary region relative to the jaw and skull to correct for maxillary hypoplasia, where the upper lip and/or nose are depressed relative to the remainder of the face structure. In this case the osteotomy may be performed across the maxilla to the nasal cavity, and a pair of distractors is affixed across the osteotomy gap by attaching bone plates to the bone segments with mechanical fasteners. Gradual incremental extension of the distractors, i.e., separation of the bone plates, advances the anterior maxillary segment relative to the posterior maxillary segments while bone regeneration fills in the osteotomy gap. When the proper position is achieved, distraction is halted. After sufficient regeneration and healing, the distractors are removed.
Because the distractors are typically positioned within or covered by tissue, it is often necessary to elongate the main body of the distractor in the proximal direction or alternatively to connect an extension actuator arm to the distraction mechanism that is exposed and easily accessible to the doctor, surgeon or technician when the device needs to be actuated. Providing an elongated main body is not an optimal solution, as the distraction device must remain in the patient until healing as completed and the extended portion now serves no function. Known extension arms are not optimal either, as the mechanism for attachment and detachment of the extension arm from the main body is usually covered by tissue, such that dissection of tissue is required to expose the detachment mechanism in order to remove the arm after the distraction process has been completed but before the distraction device may be removed from the patient.
It is an object of this invention to provide a releasable and removable actuator arm, primarily for a craniofacial maxillary type distraction device, whereby the actuator arm may be easily and rapidly released and removed from the patient once final distraction has occurred, such that only the distractor operative mechanism and bone plates remain in the patient during the healing process, wherein the actuator arm is releasable from the proximal end.